package com.ydj.framework.utils;

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.encoders.Base64;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.Key;
import java.security.Security;

public class WechatDecryptDataUtil {
    private static Cipher cipher;

    private static Key key;

    private static final String KEY_ALGORITHM = "AES";

    private static final String ALGORITHM_STR = "AES/CBC/PKCS7Padding";

	/**
	 * 解码数据获取 UnionId
	 *
	 * @param encryptDataB64    完整用户信息的加密数据
	 * @param sessionKeyB64     SessionKey
	 * @param ivB64             加密算法的初始向量
	 * @return                  UnionId
	 */
    public static String decryptData(String encryptDataB64, String sessionKeyB64, String ivB64) {
        return new String(
            decryptOfDiyIV(
                    Base64.decode(encryptDataB64),
                    Base64.decode(sessionKeyB64),
                    Base64.decode(ivB64)
            )
        );
    }

	/**
	 * 解密方法
	 *
	 * @param encryptedData 要解密的字符串
	 * @param keyBytes      解密密钥
	 * @param ivs           自定义对称解密算法初始向量 iv
	 * @return              解密后的字节数组
	 */
	private static byte[] decryptOfDiyIV(byte[] encryptedData, byte[] keyBytes, byte[] ivs) {
		byte[] encryptedText = null;
		init(keyBytes);
		try {
			cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ivs));
			encryptedText = cipher.doFinal(encryptedData);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return encryptedText;
	}

	private static void init(byte[] keyBytes) {
		// 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
		int base = 16;
		if (keyBytes.length % base != 0) {
			int groups = keyBytes.length / base + (keyBytes.length % base != 0 ? 1 : 0);
			byte[] temp = new byte[groups * base];
			Arrays.fill(temp, (byte) 0);
			System.arraycopy(keyBytes, 0, temp, 0, keyBytes.length);
			keyBytes = temp;
		}
		// 初始化
		Security.addProvider(new BouncyCastleProvider());
		// 转化成JAVA的密钥格式
		key = new SecretKeySpec(keyBytes, KEY_ALGORITHM);
		try {
			// 初始化cipher
			cipher = Cipher.getInstance(ALGORITHM_STR, "BC");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static String decodeMobile(String encryptDataB64, String sessionKeyB64, String ivB64) {
		String mobileData = WechatDecryptDataUtil.decryptData(encryptDataB64, sessionKeyB64, ivB64);
		ExJsonObject jsonMobile = new ExJsonObject(mobileData);
		return jsonMobile.optString("purePhoneNumber");
	}
}